1. Field of the Invention
The present invention relates to a method for producing a cathode active material having a layered rock salt structure for a lithium secondary battery.
2. Description of the Related Art
Cobalt-based cathode active materials are widely used as materials for producing a cathode of a lithium secondary battery (may be referred to as a lithium ion secondary battery). Such cobalt-based cathode active materials (typically, LiCoO2) have a so-called α-NaFeO2 type layered rock salt structure. In the cobalt-based cathode active materials, intercalation and deintercalation of lithium ions (Li+) occur through crystal planes other than the (003) plane (i.e., lithium ion intercalation/deintercalation planes, e.g., the (101) plane and the (104) plane). Through such intercalation and deintercalation of lithium ions, charge and discharge are carried out.
As used herein, the term “layered rock salt structure” refers to a crystal structure in which lithium layers and layers of a transition metal other than lithium are arranged in alternating layers with an oxygen layer therebetween; i.e., a crystal structure in which transition metal ion layers and lithium layers are arranged in alternating layers via oxygen ions (typically, α-NaFeO2 type structure: cubic rock salt type structure in which transition metal and lithium layers are arrayed orderly in the direction of the [111] axis).